1. Field of the Invention
This invention relates to an ice-making machine having a thermal relay, and more particularly to an automatic ice-making machine, for use in a refrigerator, which has a thermal relay for detecting the temperature of an ice-making tray in order to repeat the ice-making operation.
2. Description of the Prior Art
FIG. 1 shows an ice-making machine. In FIG. 1, reference numeral 1 designates an ice-making tray, 2 is a control box arranged at one side of the ice-making tray 1, 3 is a thermal relay disposed in the control box 2 so as to be brought into intimate contact with the ice-making tray 1, 4 is a rotary shaft for separating ice pieces made in the ice-making tray 1, and 5 is a water supply port for supplying water into the ice-making tray 1.
In such a conventional ice-making machine, water is supplied to the ice-making tray 1 through the water supply port 5 and transformed into ice by cooled air in the refrigerator. When the temperature of the ice is lowered to a predetermined value, the lowered temperature is detected by the thermal relay 3 so that a motor (not shown) is turned on and the rotary shaft 4 thereof is rotated. As a result, the ice pieces are pushed away from the ice-making tray 1 by the rotary shaft.
In such an operation, it is very important that the thermal relay 3 can detect temperature with a high precision and, accordingly, it is necessary to pay close attention when the thermal relay 3 is mounted to the ice-making tray 1.
FIGS. 2 to 7 illustrate a conventional mounting arrangement of the thermal relay. In the method shown in FIGS. 2 and 3, the thermal relay 3 is inserted into a case 6b having mounting arms 6a and molded with plastic materials. Each of the arms 6a is fixed to the control box 2 by means of a screw 7 to bring a temperature sensing portion of the thermal relay 3 into contact with the ice-making tray 1. In this case, the effective length of the arm 6a becomes small because a portion of the arm 6a is fixed to the control box 2 by the screw. Thus, the spring constant of the arm 6a becomes relatively large.
In the arrangement shown in FIGS. 4 and 5, the thermal relay 3 is fixed to the control box 2 by a screw 7 through a spring plate 6c. In this case, the mounting of the thermal relay is unstable, so that a spring plate having a relatively large spring constant must be used.
In the arrangement shown in FIGS. 6 and 7, the thermal relay 3 is inserted into a concave portion 8 formed on an outer wall of the control box 2. A spring plate 6d in the form of wedge is inserted between the concave portion 8 and the outer wall to fix the thermal relay 3 to the concave portion 8. In this case, the spring plate 6d cannot be long, because it must be inserted into a relatively narrow space. Further, because the spring plate 6d is formed separately from the thermal relay 3, a great deal of skill is required to assemble them.
As stated above, the conventional ice-making machine has so many drawbacks that the space required for mounting the thermal relay is limited. Accordingly, when the thermal relay is mounted, much time and skilled labor are required in order to maintain constant a contact pressure of the thermal relay against the ice-making tray. This is because a dimensional error of the thermal relay mounting portion affects to a large extent the contact pressure of the thermal relay, particularly if the spring constant is set large in order to obtain high mounting forces.
Further, if the contact pressure of the thermal delay is too large, the temperature sensing portion of the thermal relay is deformed and the setting temperature is varied. On the other hand, a temperature detection error becomes large if the contact pressure is too small.